1. Field of the Invention
This invention relates to a vascular clamp assembly, and more particularly relates to an adjustable, variable closure force microvascular clamp.
2. Description of the Prior Art
For years, surgeons and others have strived to design the ideal microvascular clamp for temporary vascular occlusion. Such a clamp should be easy to apply to the vessel, atraumatic and have a closing pressure that is sufficient to prevent bleeding and accidental displacement--in other words, a clamp that can occlude the vessel without crushing it.
Conventional surgical clamps for temporary occlusion come in a variety of configurations, and are either the adjustable type, having a variable closing pressure, or the pre-fixed type, having a closure force set by the manufacturer. Each type has its disadvantages.
Logistical problems are often encountered in the operating room when the surgeon elects to perform vascular surgery using the latter, pre-fixed type of clamp, as the operating room must be outfitted, preparatory to surgery, with a vast array of clamps, graduated in size and closure force.
Furthermore, the selection of the proper clamp is quite subjective, even if its closure force is known. Oftentimes, the gradation in available clamp sizes and manufacturer set tensions does not accommodate the surgeon's immediate needs, and he may be forced to choose between an excessively strong or oversized clamp, which may severely injure the blood vessel, and an undersized clamp with insufficient closure force, which may slip from the vessel or not provide the desired vascular occlusion.
For these reasons, many surgeons prefer to use clamps with an adjustable closure force.
One often used adjustable type clamp, commonly referred to as the Henderson clamp-approximator, basically consists of two clamps interconnected by a sliding tube system. Each clamp includes overlying blades between which the vessel is received. The blades apply an adjustable clamping force to the vessel that is regulated by a cylindrical key.
Although suitable for many applications, the Henderson clamp-approximator has a number of disadvantages. First, the closing pressure of the clamps cannot be finely adjusted, and the surgeon may inadvertently crush small vessels with this device.
Second, the Henderson apparatus is difficult to apply, as the surgeon must hold the clamp in one hand, the adjustment key in the other, and maneuver the vessel between the blades with a third hand.
Third, the need to screw the clamps shut rather than clip them onto the vessel makes the Henderson clamp-approximator awkward to use.
Another microvascular surgical clip having an adjustable, variable closure force is described in the Journal of Microsurgery, Volume 3, Winter Issue, 1981, pages 89-91. The clip includes a resilient annular body which extends into a pair of cooperating, vessel engaging blades. A narrow channel with three enlargements is formed in the annular body of the clip. A spring is secured at one of its ends to the inner surface of the annular body on the opposite side of the channel, and extends across the interbody space, where its other end is secured to an adjustable pin slidably mounted within the channel. The spring's tension is adjusted by moving the pin into the various enlargements of the channel. Adjustment of the spring affects the closure force of the blades.
The device described above is disadvantageous to use because the coiled spring is likely to accumulate clotted blood, much more so than with other types of clamps. The clotted blood is difficult to remove, and may affect the resilience of the clip and its closure force.
A further microsurgical clip is disclosed in U.S. Pat. No. 4,337,774, which issued to Alfred Perlin. Perlin describes in his patent a surgical clip design having a pair of integrally joined arms, each of which terminate in a flat jaw. The arms are formed of springy material and are outwardly sprung. The first arm includes a cam track formed with a number of detents on its outer surface. A resilient rod is mounted cantilever-fashion on the second arm, and has a cam follower at its end which rides on the cam track to bring the jaws into a desired degree of clamping force with a blood vessel.
The Perlin clip disclosed in the above-identified U.S. patent is suitable for use in many applications, although, like other conventional clamps described previously, presents a number of disadvantages in its use. One major disadvantage is that the cam track formed on one of the arms is exposed. The detents formed in the cam track may accumulate blood which may not only affect the closure force of the clip, but also prevent the cam follower from properly engaging the detent. The cam follower may in fact slip out of the selected detent and into an undesired location on the cam track, which may affect the closure pressure of the vessel holding jaws.
Additionally, the cam follower extends considerably beyond the interior area of the clip. The cam follower thus remains exposed and unprotected. Because of the confined space in which to work, the surgeon may inadvertently dislodge the cam follower from its selected detent which of course may increase or decrease the closure force of the jaws on the vessel.